1. Field of the Invention
The present invention relates to apparatus for detecting and measuring peak-to-peak values in electrical signals. More particularly, the present invention relates to apparatus capable of detecting and measuring peak-to-peak values in electrical signals comprising at least one positive-going and one negative-going peak.
2. Description of the Prior Art
The detection and measurement of peak-to-peak values in electrical signals has always been of interest to provide information about the signal itself, the source generating the signal, or possibly the transmission system wherein the signal propagates. The conventional implementation of a peak-to-peak detecting and measuring circuit comprises, (a) a positive peak detector and a negative peak detector for respectively measuring the magnitude of the positive peak and negative peak of an input waveform with respect to a d.c. reference voltage; and (b) a circuit to sum the magnitude of the two measured peaks to provide a peak-to-peak value. The inherent response time and signal tracking errors associated with such circuits, however, makes this type of circuitry unsuitable for use in detecting and measuring peak-to-peak values of waveforms comprising short duration and fast rise time pulses.
Waveforms comprising short duration and fast rise time pulses can, for example, be found in high frequency signals such as stress waves generated by a crack or a flaw in a brittle material which is under a load. Typical circuitry for detecting and measuring stress waves is disclosed in U.S. Pat. No. 3,713,127, issued to F. C. Keledy et al. There a peak detector and integrator circuit detects the envelope of an analog signal to charge a capacitor to a peak signal proportional to the amplitude of the envelope. This circuit, however, does not measure peak-to-peak voltages, but only indicates the magnitude of the detected acoustic energy by tracking the upper half of the envelope of the analog signal.
A subsisting problem is to provide improved method and apparatus for detecting and measuring peak-to-peak values in electrical signals comprising at least one positive-going and one negative-going peak, and especially signals also including waveforms having short duration and fast rise time pulses.